Next… Since we know some of the habitats and organisms that live in marine environments, we can also study their interactions (w/ each other and w/i the community structure)

Ecology is the study of the inter-relationships between the physical and biological aspects of the environment. It is the study of how organisms adapt to and alter their environment.

Marine Ecology Ecology is the interaction between organisms and their environment. These interactions affect the survival and distribution of these organisms. Interactions can be very complex.

Ecosystem All the biotic (living) and abiotic (nonliving) components in a defined area. Ecosystems interact. All ecosystems require a constant input of energy. Chemicals and nutrients are cycled within ecosystems.

Population A group of organisms of the same species occupying a specific area Community All populations of organisms living in a defined area. Habitat The physical place where an organism lives. Niche The resources (biotic & abiotic) an organism uses for survival, growth, and reproduction.

A Biological Community is “all of the populations of organisms living together (and potentially interacting) within the ecosystem.”

Community Composition Physical factors (abiotic) – temperature, salinity, dessication, pressure (etc.) – can all limit where an organism can survive Biological factors (biotic) – larval supply, competition, predation, parasitism – can also limit where an organism can be found

Some (physical, abiotic) environmental factors in the marine environment we mentioned include: – Temperature – Salinity – Pressure – Nutrients – Dissolved gases – Currents – Light – Suspended sediments – Substrate (bottom material) – River inflow (estuaries) – Tides – Waves

Physical Factors range of tolerance Steno = narrow Eury = wide or broad Examples: – stenothermal or eurythermal – stenohaline or euryhaline

Needs of a Species Populations demand specific resources to survive. These resources can affect population growth if they are in short supply. These resources that have the ability to affect the growth of a population are called limiting resources. Thus your ABIOTIC FACTORS can be limiting!

Needs of a Species Even if an organism is able to acquire a limiting resource, there is a maximum number of organisms that any habitat can support. This number is known as the carrying capacity. As a population becomes more “crowded,” the growth rate of that population will decrease.

Unrestrained Growth: unrealistic because we have limiting resources & biotic factors influencing survival

Marine Ecology Ways that Species can Interact (i.e. the BIOTIC FACTORS): 1.Competition 2.Predator-Prey Interactions (a type of competition) 3.Symbiosis 4.Larval Supply

Competition An organism can use a resource at the expense of another organism. This may result in reduced ability of that individual to reproduce or even survive. Poorer competitors may die out due to this competition.

Competition Competition occurs when organisms must “fight” with one another over a limiting resource they both require for survival. Organisms can compete with members of their own species – intraspecific competition – or members of other species – interspecific competition.

Competition limited supply of resources Intraspecific competition – between individuals of the same species – Leads to adaptation Interspecific competition – between individuals of different species – may lead to competitive exclusion

2 Hermit crabs fight (compete) over a snail shell – a new “home”

Competition Can lead to ADAPTATION by 1 organism or many Can make organisms “adapt” their behaviors (acting differently), “adapt” physically (develop different physical attributes to enhance their chances of survival – large mouth/no teeth in a whale shark)

Figure 10.6

Interspecific Competition Individuals of different species compete for same resources (food, shelter, space). What are possible outcomes of interspecific competition? one individual excludes the other (principle of competitive exclusion) they coexist (resource partitioning)

Interspecific Competition (Competitive Exclusion): Balanus cannot withstand the currents, temp. differential and dessication that Chthamulus can thus Balanus “prefers” lower limits. Balanus is larger and, during larval recruitment, has a much better chance of survival (& colonization) on rock ZONATION leads to Balanus outcompeting Chthamulus in lower tidal ranges but Chthamulus can still live in upper zone

Interspecific Competition (Competitive Exclusion): Balanus upper and lower limit(s) thus set by PHYSICAL factors Chathamulus lower limit thus set by BIOLOGICAL factors (competition – for space during larval recruitment) and upper limit thus set by PHYSICAL factors (out of intertidal zone = death)

Resource partitioning (interspecific competition, part 2)- Competing species can coexist if they use the same resource in a slightly different way or at a different time. Space on a rock (a habitat) Food (not enough of 1 kind for all) The species must adapt to use a different space or eat something different…but TOGETHER. It is a division of resources!

Resource Partitioning

Symbiosis - one species living in or on another. The co- occurrence of two species in which the life of one is closely tied with the life of another. Types of Symbiosis: 1. Mutualism (++) both species benefit (example: cleaning associations, clown fish, zooxanthelle, cleaner shrimp). 2. Commensalism (+0) one species benefits with no apparent effect on the other (example: barnacles living on whales, pilotfish & shark). 3. Parasitism (+-) one species benefits & the other is harmed (examples: tapeworms in the guts of whales, roundworms).

More on Symbiosis If partners if a symbiotic relationship can live without one another, this is known as facultative symbiosis. If the partners cannot survive with the other partner, this is known as obligate symbiosis. In all cases, the smaller partner is known as the symbiont and the larger partner is called the host.

Page 218

Figure 10.10

Figure 10.9

Nematode. Credit: © Carolina Biological/Visuals Unlimited

Fig. 16.8e Elephantitis from a parasitic nematode

Guinea worm (parasitic nematode) removed

Predation One species (predator) kills another (prey) for food. Can also affect community structure Allows for increased diversity when superior competitor is preferred prey Prey species often have adaptations that help them avoid being eaten such as: Warning coloration (the opposite of camoflage!) Camouflage Mimicry

Flamboyant Cuttlefish Warning Coloration “warns” predators it’s poisonous!

Camouflage

Mimicry – top snake is venomous, a coral snake; bottom snake is not (a red milk snake) but they share the same colors!

Larval Supply: Larval supply is a biotic factors influencing community ecology but… Many factors effect larval survival (both abiotic & biotic) Larval spawning typically occurs when food resources are expected to be highest (biotic) Larval spawning typically occurs when conditions are best (such as seasonal and temperature conditions) (abiotic)

Larval Supply cont.: Remember: The BIOTIC FACTORS come “full circle” here…competition (remember competitive exclusion and zonation!) effects where larvae can settle and (heavy) predation can decrease larval supply before they even get the chance! So…which comes 1 st ? The chicken or the egg?

Unrestrained Growth: unrealistic because we have limiting resources & biotic factors influencing survival

Complete “Study” of Ecology is: Combination of “Environmental” Factors: – biotic factors – abiotic factors (+) Placing them (the organisms) in the population/community (+) The specific habitat (where an organisms lives) = NICHE!

1 example of a “habitat”

Study of Ecology Niche: an organism’s environmental role – environmental factors – biological factors – the organism’s behavior